Filtration devices and systems are employed in a wide range of applications for filtering contaminants from various process fluids. For example, it is known to pass air or similar gasses through filter assemblies that enclose filtration media such as filter paper to remove dust and other contaminants. The filtration media is typically enclosed within a housing that is permanently fixated within a larger overall process system that utilizes the filtered air or gas. The filter media is often configured into a filter element or filter cartridge that can be removably received within the housing to remove the containments from the fluids or gasses flowing therein. Because of the potential for a single or primary filter element to be displaced or fail, and to prevent dislodged debris during installation or removal of the primary filter from entering the engine, it is known to provide a second or safety filter element typically downstream of the primary filter element.
One method of constructing such safety filter elements, as taught in U.S. Pat. No. 6,221,122 to Gieseke et al., herein incorporated by reference, involves a rigid support frame for supporting and retaining a planar sheet of flexible filter media. The planar sheet includes a skirt that is folded between the peripheral edge of the frame and an inner surface of the filter housing for creating a sealing effect therebetween and ensuring that process fluids and gasses flow through the safety filter element. The skirt when folded during slidable insertion of the filter element into the filter housing provides the potential for leak paths past the safety filter element.